AMASTRA, KAUAI. 143 



conic, more or less ribbed embryonic whorls ; also Carelia and 

 typical Amastra (magna group) have similar embryos. In 

 color and texture the adult shell resembles Amastrella an- 

 thonii, etc. ; while the resemblance to Cyclamastra is discussed 

 below. The possession of features belonging to several Amas- 

 tran groups favors the view that Kauaia is an old form, little 

 changed since it arose from the primitive Amastran stock. 



"The resemblance between the neanic stages of Kauaia 

 kauaiensis and the adults and older stages of Cyclamastra 

 cyclostoma are visible in the flattened, carinated and rapidly 

 spreading volutions of the young of kauaiensis through the 

 first five volutions. After this the increase by growth is less 

 rapid in the transverse diameter of the spire, and the outer 

 or dorsal side begins to take on a different aspect. The con- 

 tour becomes more or less curved and the spire more elon- 

 gated owing to the greater increase of the vertical or dorso- 

 ventral diameters. Not only the form, but the open umbilicus 

 at this stage, as well as the eolumella and aperture, are gener- 

 ically identical with those of Cyclamastra. Later the close 

 eolumella and changes of form above described show a wider 

 separation in structure. It is also obvious from the above 

 that Cyclamastra is nearer to the forms from which Kauaia 

 kauaiensis was derived than the full-grown shells of that 

 species, and must therefore be looked upon as more primitive. 

 The resemblances of the younger stages of kauaiensis to the 

 full-grown stages of C. cyclostoma are not as strongly pro- 

 nounced in some shells as in others, owing to the fact that 

 the young have more elongated spires in some shells. " 

 (Hyatt MS.) 



1. A. KAUAIENSIS (Newcoinb). PL 16, figs. 1, 2, 3. 



The shell is imperforate, dextral, trochiform, solid, carinate. 

 The first whorl is smooth (worn in examples seen) ; the sec- 

 ond is rather coarsely, arcuately ribbed; third whorl more 

 finely ribbed ; succeeding whorls are rudely obliquely wrinkle- 

 striate. On the fourth whorl spiral sculpture appears, at first 

 fine, later becoming rather coarse but very low spiral cords. 

 The whorls are very strongly keeled, the keel appearing above 



